Objective: To examine the effect of intensive therapy on neuropsychological performance in patients who participated in the Diabetes Control and Complications Trial (DCCT).
Design: Multicenter, randomized, controlled clinical trial.
Setting: 29 DCCT clinical centers.
Patients: 1441 patients with insulin-dependent diabetes mellitus (IDDM) between 13 and 39 years of age who had had IDDM for 1 to 15 years and had no or minimal retinopathy or nephropathy at baseline. Volunteers were excluded if they had a history of substance abuse, psychological disturbance, or recurrent hypoglycemia with coma or seizure.
Intervention: Intensive therapy with 3 or more daily insulin injections or continuous subcutaneous insulin infusion, guided by 4 or more glucose tests per day, compared with conventional therapy with 1 or 2 daily insulin injections.
Outcome measures: Neuropsychological assessments were done at baseline; years 2, 5, and 7; and the end of the study. Eight cognitive domain scores were developed from the test results and were used to identify patients whose neuropsychological performance had clinically worsened.
Results: Intensive therapy did not affect neuropsychological performance. In addition, patients who had repeated episodes of hypoglycemia did not perform differently than patients who did not have repeated episodes.
Conclusion: Intensive therapy and the attendant risk for hypoglycemia were not associated with neuropsychological impairment in the DCCT.